1. Field of the Invention
This invention relates to a light emitting device and a method for manufacturing the same.
2. Background Art
A light emitting device with high brightness is required, for example, in illumination devices, LED displays, and backlight sources for image displays capable of emitting light in visible to infrared wavelength ranges.
The light in visible to infrared wavelength ranges emitted from an InAlGaP-based light emitting layer is absorbed in GaAs of the substrate, and the brightness decreases. Hence, a crystal growth layer including a light emitting layer that is easily lattice matched with GaAs, and a GaP substrate that is lattice mismatched with GaAs but translucent, are laminated illustratively using a wafer bonding process to provide a structure achieving high brightness.
Furthermore, high brightness requires a chip structure for increasing the external light extraction efficiency and internal efficiency. Among them, the light extraction efficiency is increased by using a structure in which an ITO (indium tin oxide) or other transparent electrode is provided on the chip surface. However, the ITO or other transparent electrode has the problems of low light transmittance and having difficulty in achieving good ohmic contact.
JP-A-2002-164574 (Kokai) discloses a technique related to a high-power light emitting device with enhanced external quantum efficiency. In this technique, a light extraction window is etched, which is shaped like an elongated rectangle as viewed from the upper surface of the device. The end surface of the light emitting section is exposed to the recessed sidewall formed by etching and improves the external light extraction efficiency.
However, in this technique, the recess needs to be etched more deeply than the light emitting layer, thus complicating the manufacturing process. Furthermore, exposure of the end surface and its neighborhood of the light emitting section is likely to cause such problems as the crystal surface being prone to degradation.